Production of Gears by sintering process is a method for making gears from powder, by heating the material (below its melting point - solid stage sintering) until its particles adhere to each other.
Sintering is traditionally used for manufacturing ceramic objects, and has also found uses in such fields as powder metallurgy.
A special form of sintering, not limited the solid state but still considered part of powder metallurgy is liquid state sintering in which at least one but not all elements are existing in a liquid state. Liquid state sintering is required for making cemented carbides or tungsten carbide.
Sintered bronze in particular is frequently used as a material for bearings, since its porosity allows lubricants to flow through it or remain captured within it. In the case of materials with high melting points such as Teflon and tungsten, sintering is used when there is no alternative manufacturing technique. In these cases very low porosity is desirable and can often be achieved.
Metallurgists can sinter most, if not all, metals. This applies especially to pure metals produced in vacuum which suffer no surface contamination. Many nonmetallic substances also sinter, such as glass, alumina, zirconia, silica, magnesia, lime, ice, beryllium oxide, ferric oxide, and various organic polymers.
Sintering, with subsequent reworking, can produce a great range of material properties. Changes in density, alloying, or heat treatments can alter the physical characteristics of various products.
For instance, the tensile strength En of sintered iron powders remains insensitive to sintering time, alloying, or particle size in the original powder, but depends upon the density of the final product according to:
En/E = (D/d)3.4
where D is the density, E is Young's modulus and d is the maximum density of iron.